X-ray microanalyzers use an X-ray beam to irradiate a small spot on a sample. The microanalyzer then detects X-rays that are emitted from the spot, by reflection, scattering or fluorescence, in order to determine properties of the sample with fine spatial resolution.
For example, U.S. Pat. No. 6,108,398, whose disclosure is incorporated herein by reference, describes an X-ray microfluorescence analyzer. A sample is irradiated with X-rays through a polycapillary optic, which focuses the X-ray beam to a spot about 50 μm in diameter. Multiple X-ray detectors, such as silicon PIN diodes, are arranged in a ring, centered over the spot, in order to capture the emitted fluorescent photons over a large range of angles. The X-ray detectors produce electrical signals in response to the incident photons. These signals are analyzed in order to determine the spectrum and intensity of the X-ray photons, which are indicative of characteristics of the sample at the spot, including its composition and layer thickness. The sample may be scanned horizontally relative to the analyzer (or the analyzer may be scanned over the sample) in order to measure the microfluorescence at different points on the sample.